Recently, an electric wire or cable, which has resistance to termite and/or rodent, is required.
In order to meet with such a requirement, a conventionally known electric wire or cable is covered by extrusion coating of a covering material, the chief ingredient of which material is a synthetic resin or a synthetic rubber and which material contains a termite repellent and/or a rodent repellent.
For example, in a typical method for manufacturing a conventionally known termite resistant cable, a master batch is previously prepared by mixing a termite repellent with synthetic resin or synthetic rubber. Termite repellent is, for example, copper naphthenate, organic phosphate, carbamate insecticide, or pyrethroids. The synthetic resin is, for example, polyvinyl chloride, or polyethylene. The synthetic rubber is, for example, chloroprene rubber.
The master batch thus prepared is mixed at a predetermined ratio with coating material. The thus obtained mixture is extruded onto a cable by extrusion coating to form a conventional termite resistant cable.
When a covering material, the chief ingredient of which is a synthetic resin or a synthetic rubber and which contains a termite repellent and/or a rodent repellent, is extruded onto a cable, the termite repellent and/or a rodent repellent is often vaporized or heat decomposed by the heat of a high temperature, i.e., between about 160.degree. and 220.degree. C., generated during extrusion coating. Accordingly, the percentage of retension of the repellent in the coating is low. The percentage of retension described above is defined as the percentage of the amount of the repellent retained in the product to that of the repellent added to the raw material.
Consequently, if a sufficiently high termite resistant effect or rodent resistant effect is necessary, a large amount of termite repellent and/or rodent repellent must be added.
As a result, the following problems are observed in the conventional termite and/or rodent resistant cable. Since the termite repellent and rodent repellent are expensive, the cost for manufacturing such a conventional termite and/or rodent resistant cable is high. Further, since the termite repellent and rodent repellent are easily heat decomposed, the heat resisting characteristic of the conventional termite and/or rodent resistant cable is low. Similarly, the mechanical characteristic of the termite and/or rodent resistant cable is low. Furthermore, since the termite repellent and rodent repellent are easily heat vaporized, the working environment for manufacturing the conventional termite and/or rodent resistant cable is bad.
Under these circumstances, I have previously invented a process for producing a smelling synthetic resin product which comprises forming a cyclodextrin inclusion compound consisting of a perfume included in cyclodextrin, drying and powdering the obtained cyclodextrin inclusion compound and mixing the obtained powder with a synthetic resin compound (cf. Japanese Pat. No. 1090861).
I have further invented a process for producing an insectifugal and insecticidal film which comprises forming a cyclodextrin inclusion compound consisting an insectifugal and insecticidal agent included in cyclodextrin, drying and powdering the obtained cyclodextrin inclusion compound and mixing the obtained powder with a synthetic resin compound followed by molding into a film (cf. Japanese Patent Laidopen No. Sho 61-65805 and Japanese Patent Laid-open No. Sho 61-137803).
A smelling synthetic resin product produced by forming a cyclodextrin inclusion compound consisting of a perfume included in cyclodextrin, powdering and drying the obtained cyclodextrin inclusion compound and mixing the obtained powder with a synthetic resin compound is much more excellent than those produced by conventional methods. Subsequent studies have proved that not only perfumes but also various substances such as insectifuges, mildewproofing agents and rust preventives may be formed into a cyclodextrin inclusion compound so long as it can be included in cyclodextrin to thereby produce synthetic resin products having the effect of each substance.
However, these cyclodextrin inclusion compounds consisting of a perfume included in cyclodextrin cannot be used in practice in synthetic resin products of a high molding temperature, i.e., 180.degree. C. or above. Cyclodextrin per se is stable at high temperatures and shows no chemical change so that it is theoretically possible to use it in a synthetic resin of a high molding temperature. However, pure cyclodextrin is so expensive that decomposed starches containing cyclodextrin are employed in practice. These decomposed starches contain reducing sugars which would be taken place chemical change and charred when molded at a high temperature.
Although there is no problem in the production of a synthetic resin product having various effects by forming a cyclodextrin inclusion compound consisting of perfume(s), insectifuge(s), or rust preventive(s) included in cyclodextrin, drying and powdering the obtained cyclodextrin inclusion compound and mixing the obtained powder with a synthetic resin compound on a laboratory scale with the use of pure cyclodextrin, there remains a problem to be solved in the production thereof on an industrial scale.
In addition, the volatility of each substance is somewhat depressed by including the same in cyclodextrin to thereby form a cyclodextrin inclusion compound, which allows its effect to persist for a much longer period than with conventional products. However, the persistence is somewhat insufficient yet.